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Message-ID: <510B7DC6.10803@jp.fujitsu.com>
Date: Fri, 1 Feb 2013 17:33:10 +0900
From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To: Ming Lei <ming.lei@...onical.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
<linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>,
Felipe Balbi <balbi@...com>, <stable@...r.kernel.org>
Subject: Re: [PATCH] block: partition: optimize memory allocation in check_partition
2013/02/01 12:07, Ming Lei wrote:
> Currently, sizeof(struct parsed_partitions) may be 64KB in 32bit arch,
> so it is easy to trigger page allocation failure by check_partition,
> especially in hotplug block device situation(such as, USB mass storage,
> MMC card, ...), and Felipe Balbi has observed the failure.
>
> This patch does below optimizations on the allocation of struct
> parsed_partitions to try to address the issue:
>
> - make parsed_partitions.parts as pointer so that the pointed memory
> can fit in 32KB buffer, then approximate 32KB memory can be saved
>
> - vmalloc the buffer pointed by parsed_partitions.parts because
> 32KB is still a bit big for kmalloc
>
> - given that many devices have the partition count limit, so only
> allocate disk_max_parts() partitions instead of 256 partitions
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Ming Lei <ming.lei@...onical.com>
> ---
> block/partition-generic.c | 2 +-
> block/partitions/check.c | 35 ++++++++++++++++++++++++++++++-----
> block/partitions/check.h | 4 +++-
> 3 files changed, 34 insertions(+), 7 deletions(-)
>
> diff --git a/block/partition-generic.c b/block/partition-generic.c
> index f1d1451..043d0bd 100644
> --- a/block/partition-generic.c
> +++ b/block/partition-generic.c
> @@ -525,7 +525,7 @@ rescan:
> md_autodetect_dev(part_to_dev(part)->devt);
> #endif
> }
> - kfree(state);
> + release_partitions(state);
> return 0;
> }
Do you check all kfree(state)?
# block/partition-generic.c
414 int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
415 {
416 struct parsed_partitions *state = NULL;
417 struct hd_struct *part;
418 int p, highest, res;
419 rescan:
420 if (state && !IS_ERR(state)) {
421 kfree(state);
422 state = NULL;
423 }
At least, you should use release_partitions() instead of kfree() here.
Thanks,
Yasuaki Ishimatsu
>
> diff --git a/block/partitions/check.c b/block/partitions/check.c
> index bc90867..86c9450 100644
> --- a/block/partitions/check.c
> +++ b/block/partitions/check.c
> @@ -14,6 +14,7 @@
> */
>
> #include <linux/slab.h>
> +#include <linux/vmalloc.h>
> #include <linux/ctype.h>
> #include <linux/genhd.h>
>
> @@ -106,18 +107,43 @@ static int (*check_part[])(struct parsed_partitions *) = {
> NULL
> };
>
> +static struct parsed_partitions *allocate_partitions(int nr)
> +{
> + struct parsed_partitions *state;
> +
> + state = kzalloc(sizeof(*state), GFP_KERNEL);
> + if (!state)
> + return NULL;
> +
> + state->parts = vzalloc(nr * sizeof(state->parts[0]));
> + if (!state->parts) {
> + kfree(state);
> + return NULL;
> + }
> +
> + return state;
> +}
> +
> +void release_partitions(struct parsed_partitions *state)
> +{
> + vfree(state->parts);
> + kfree(state);
> +}
> +
> struct parsed_partitions *
> check_partition(struct gendisk *hd, struct block_device *bdev)
> {
> struct parsed_partitions *state;
> int i, res, err;
>
> - state = kzalloc(sizeof(struct parsed_partitions), GFP_KERNEL);
> + i = disk_max_parts(hd);
> + state = allocate_partitions(i);
> if (!state)
> return NULL;
> + state->limit = i;
> state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
> if (!state->pp_buf) {
> - kfree(state);
> + release_partitions(state);
> return NULL;
> }
> state->pp_buf[0] = '\0';
> @@ -128,10 +154,9 @@ check_partition(struct gendisk *hd, struct block_device *bdev)
> if (isdigit(state->name[strlen(state->name)-1]))
> sprintf(state->name, "p");
>
> - state->limit = disk_max_parts(hd);
> i = res = err = 0;
> while (!res && check_part[i]) {
> - memset(&state->parts, 0, sizeof(state->parts));
> + memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
> res = check_part[i++](state);
> if (res < 0) {
> /* We have hit an I/O error which we don't report now.
> @@ -161,6 +186,6 @@ check_partition(struct gendisk *hd, struct block_device *bdev)
> printk(KERN_INFO "%s", state->pp_buf);
>
> free_page((unsigned long)state->pp_buf);
> - kfree(state);
> + release_partitions(state);
> return ERR_PTR(res);
> }
> diff --git a/block/partitions/check.h b/block/partitions/check.h
> index 52b1003..4fefdbb 100644
> --- a/block/partitions/check.h
> +++ b/block/partitions/check.h
> @@ -15,13 +15,15 @@ struct parsed_partitions {
> int flags;
> bool has_info;
> struct partition_meta_info info;
> - } parts[DISK_MAX_PARTS];
> + } *parts;
> int next;
> int limit;
> bool access_beyond_eod;
> char *pp_buf;
> };
>
> +void release_partitions(struct parsed_partitions *state);
> +
> struct parsed_partitions *
> check_partition(struct gendisk *, struct block_device *);
>
>
--
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